Multi-Axial Bone Anchor Assembly

Abstract

In one aspect, a bone anchor assembly is provided. The bone anchor assembly includes a bone anchor, a crown member, a saddle, and a sleeve. The bone anchor assembly is configured such that the bone anchor is moveable with respect to the saddle when the sleeve is positioned around the saddle and the bone anchor is locked relative to the saddle by compression of the head portion of the bone anchor between the crown member and a seat of the saddle. In another aspect, a system for orthopedic implantation is provided. The system includes an elongated member, a compression member, and a bone anchor assembly. In another aspect, a method of assembling a bone anchor assembly is provided.

1 - 25 . (canceled) 
   
   
       26 . A bone anchor assembly, comprising:
 a bone anchor having a head portion and a bone engaging portion;   a crown member shaped and sized to mate with the head portion of the bone anchor;   a saddle having an upper portion and a lower portion and a longitudinal axis extending between the upper and lower portions,
 the upper portion having a channel for receiving an elongated member, 
 the lower portion having a bottom opening configured to receive the crown member and the head portion of the bone anchor therein, the lower portion movable between a first position for receiving the crown member and the head portion of the bone anchor and a second position for movably maintaining the crown member and the head portion of the bone anchor within the lower portion of the saddle, wherein in the first position an outer surface of the lower portion extends at an oblique angle with respect to the longitudinal axis and wherein in the second position the outer surface of the lower portion extends substantially parallel to the longitudinal axis; and 
   a sleeve configured for positioning around the lower portion of the saddle via upward advancement around the outer surface of the lower portion, the sleeve sized and shaped to maintain the lower portion of the saddle in the second position when positioned around the lower portion of the saddle;   wherein the bone anchor is secured in a fixed position relative to the saddle by compression of the head portion of the bone anchor between the crown member and the lower portion of the saddle.   
   
   
       27 . The assembly of  claim 26 , wherein the lower portion comprises a seat portion for interfacing with the head portion of the bone anchor. 
   
   
       28 . The assembly of  claim 27 , wherein the seat is configured to transmit forces from the head portion of the bone anchor radially outward to the sleeve when the sleeve is positioned around the lower portion of the saddle. 
   
   
       29 . The assembly of  claim 28 , wherein the seat portion comprises a tapered surface having an angle between 10 and 80 degrees relative to the longitudinal axis of the saddle. 
   
   
       30 . The assembly of  claim 29 , wherein the tapered surface has an angle of approximately 20 degrees relative to the longitudinal axis of the saddle. 
   
   
       31 . The assembly of  claim 29 , wherein the tapered surface has an angle of approximately 55 degrees relative to the longitudinal axis of the saddle. 
   
   
       32 . The assembly of  claim 26 , wherein the upper portion further comprises an inner shoulder for limiting the upward translation of the crown member. 
   
   
       33 . The assembly of  claim 26 , wherein the saddle further comprises an external shoulder for limiting the upward translation of the sleeve relative to the lower portion of the saddle. 
   
   
       34 . The assembly of  claim 26 , wherein the lower portion of the saddle includes a plurality of slots extending upwardly from a bottom surface of the lower portion. 
   
   
       35 . The assembly of  claim 34 , wherein each of the plurality of slots is bounded by an elongated relief opposite the bottom surface of the lower portion. 
   
   
       36 . The assembly of  claim 34 , wherein each of the plurality of slots is defined by a pair of surfaces, and wherein the pair of surfaces extend at an oblique angle with respect to the longitudinal axis of the saddle when the lower portion is in the first position and wherein the pair of surfaces extend substantially parallel to the longitudinal axis of the saddle when the lower portion is in the second position. 
   
   
       37 . The assembly of  claim 26 , wherein the sleeve includes a recess for mating with a projection extending from the saddle. 
   
   
       38 . The assembly of  claim 26 , wherein the lower portion further comprises a plurality of inner cutout portions configured to allow an increased range of motion between the saddle and the bone anchor. 
   
   
       39 . The assembly of  claim 38 , wherein the sleeve includes a plurality of outer cutout portions, the plurality of outer cutout portions configured to be aligned with the plurality of inner cutout portions of the lower portion to allow the increased range of motion between the saddle and the bone anchor. 
   
   
       40 . The assembly of  claim 38 , wherein the lower portion of the saddle includes a plurality of slots extending upwardly from a bottom surface of the lower portion and wherein the plurality of slots are substantially aligned with the plurality of inner cutouts of the lower portion 
   
   
       41 . A system for orthopedic implantation, comprising:
 an elongated member;   a locking member; and   a bone anchor assembly, the bone anchor assembly comprising:
 a bone anchor having a head portion and a bone engaging portion; 
 a crown member shaped and sized to mate with the head portion of the bone anchor; 
 a saddle having an upper portion and a lower portion and a longitudinal axis extending between the upper and lower portions,
 the upper portion having a channel for receiving an elongated member and an interface for receiving the locking member, 
 the lower portion having a bottom opening configured to receive the crown member and the head portion of the bone anchor therein, the lower portion movable between a first position for receiving the crown member and the head portion of the bone anchor and a second position for movably maintaining the crown member and the head portion of the bone anchor within the lower portion of the saddle, wherein in the first position an outer surface of the lower portion extends at an oblique angle with respect to the longitudinal axis and wherein in the second position the outer surface of the lower portion extends substantially parallel to the longitudinal axis; and 
 
 a sleeve configured for positioning around the lower portion of the saddle via upward advancement around the outer surface of the lower portion, the sleeve sized and shaped to maintain the lower portion of the saddle in the second position when positioned around the lower portion of the saddle; 
   wherein the bone anchor is secured in a fixed position relative to the saddle by compression of the head portion of the bone anchor between the crown member and the lower portion of the saddle.   
   
   
       42 . The system of  claim 41 , wherein the lower portion of the saddle includes a plurality of slots extending upwardly from a bottom surface of the lower portion, each of the plurality of slots is defined by a pair of opposing surfaces, and wherein each of the pair of opposing surfaces extends at an oblique angle with respect to the longitudinal axis of the saddle when the lower portion is in the first position and wherein each of the pair of opposing surfaces extends substantially parallel to the longitudinal axis of the saddle when the lower portion is in the second position. 
   
   
       43 . The system of  claim 42 , wherein each of the plurality of slots is bounded by an elongated relief opposite the bottom surface of the lower portion. 
   
   
       44 . The system of  claim 42 , wherein the lower portion further comprises a plurality of inner cutout portions configured to allow an increased range of motion between the saddle and the bone anchor, and wherein the sleeve includes a plurality of outer cutout portions, the plurality of outer cutout portions configured to be aligned with the plurality of inner cutout portions of the lower portion to allow the increased range of motion between the saddle and the bone anchor. 
   
   
       45 . A method of assembling a bone anchor assembly, comprising:
 providing a bone anchor having a head portion and a bone engaging portion;   providing a crown member shaped and sized to mate with the head portion of the bone anchor;   providing a saddle having an upper portion and a lower portion,
 the upper portion having a channel for receiving an elongated member, 
 the lower portion having a bottom opening configured to receive the crown member and the head portion of the bone anchor therein, the lower portion movable between a first position for receiving the crown member and the head portion of the bone anchor and a second position for maintaining the crown member and the head portion of the bone anchor within the lower portion of the saddle, wherein in the first position an outer surface of the lower portion extends at an oblique angle with respect to the longitudinal axis and wherein in the second position the outer surface of the lower portion extends substantially parallel to the longitudinal axis; 
   providing a sleeve configured for positioning around the lower portion of the saddle, the sleeve sized and shaped to maintain the lower portion of the saddle in the second position when positioned around the lower portion of the saddle;   inserting the crown member upward into the bottom opening of the lower portion of the saddle with the lower portion of the saddle in the first position;   inserting the head portion of the bone anchor upward into the bottom opening of the lower portion of the saddle with the lower portion of the saddle in the first position;   advancing the sleeve upward around the lower portion of the saddle to maintain the lower portion of the saddle in the second position, thereby movably maintaining the crown member and the head portion of the bone anchor within the lower portion of the saddle.   
   
   
       46 . The method of  claim 45 , further comprising transitioning the lower portion of the saddle from the first position to the second position after inserting the crown member and head portion of the bone anchor. 
   
   
       47 . The method  claim 46 , wherein positioning the sleeve around the lower portion of the saddle transitions the lower portion of the saddle from the first position to the second position. 
   
   
       48 . The method of  claim 46 , wherein transition the lower portion of the saddle from the first position to the second position includes transitioning a pair of opposing surfaces defining a slot in the lower portion of the saddle from a first orientation where each of the pair of opposing surfaces extends at an oblique angle with respect to the longitudinal axis of the saddle to a second orientation where each of the pair of opposing surface extends substantially parallel to the longitudinal axis. 
   
   
       49 . The method of  claim 45 , wherein positioning the sleeve around the lower portion of the saddle includes aligning a plurality of outer cutout portions of the sleeve with a plurality of inner cutout portions of the lower portion of the saddle, the inner and outer cutout portions providing an increased range of motion between the bone engaging portion of the bone anchor and the saddle. 
   
   
       50 . The method of  claim 45 , further comprising:
 positioning an elongated member within the channel of the upper portion of the saddle; and   advancing a locking member downward relative to upper portion of the saddle and into engagement with the elongated member positioned within the channel of the upper portion such that the elongated member urges the crown member into engagement with the head portion of the bone anchor, thereby fixedly securing the bone anchor relative to the saddle.